The invention relates to a washing system, and more particularly to a washing system for a windshield of a motor vehicle.
Washing systems that provide for cleaning the windshields of motor vehicles with a tank for washing water and another tank for a washing powder are known from a number of printed applications. For example, DE-OS 20 62 720 or DE-AS 29 21 158 show a washing system, wherein a pump is assigned to each of the two tanks which can be switched on independently of the other pump. In this washing system it is possible to spray only washing water, only washing powder, or washing water and washing powder together onto a windshield. If it is planned to spray washing water and washing powder always together onto the windshield, a solution with two pumps is complicated and expensive.
From DE-OS 30 15 348 a washing system is known comprising a washing pump with an impeller which can be driven in opposite directions of rotation. In case it is actuated into the one direction of rotation , only washing water from a first tank is supplied, and in case of an actuation of the impeller into the opposite direction of rotation, only washing powder from the second tank is supplied. In this washing system only one single pump is used in order to transport both fluids, however, the construction of the pump with different valves as well as the electric switch for reversing the poles of the electric motor driving the pump make this solution also relatively expensive. Furthermore, it is not possible to spray washing water and washing powder simultaneously onto a windshield, other than in a washing system with two pumps.
In DE-OS 20 62 720 a washing system is disclosed in which one pump is used for supplying both fluids. This pump takes in the two fluids via a distributing valve and the valve allows both to select between washing powder and washing water and also to select as to the mixing proportion desired for the combination of both fluids. It is possible to operate the valve manually, by motor, magnetically or also pneumatically.
A washing system is known from DE-OS 33 42 384, in the case of which a diaphragm-type or piston-type pump is assigned to the container with washing powder. When second pump (washing pump) transporting washing water is switched on, the washing powder pump is operated by the pressure of the washing water prevailing at the one side of the piston or the diaphragm, respectively, and which adds a certain amount of washing powder to the washing fluid. That means, at the beginning of a washing process a mixture of washing water and washing powder and afterwards only washing water is sprayed onto the windshield which is to be cleaned.
As described above, there are washing systems for windshields of motor vehicles, which comprise a tank for washing water and a tank for a washing powder and wherein a mixture of washing water and washing powder can be sprayed on the windshield which is to be cleaned. Also, windshield washing systems have already been suggested, in which it is exclusively possible to have washing powder and washing water as a mixture exit from the washing nozzles during the whole washing process. At first sight, it seems unnecessary in this case to provide separate tanks for the washing water and the washing powder. On the contrary, one single tank could be sufficient for the mixture. It has to be considered though that, when filling up the only existing washing fluid tank, the mixture has to be made by the owner of the motor vehicle himself or by somebody in charge. It is to be expected that in this case the optimal mixing proportions defined by the motor vehicle manufacturer, are not achieved. If there is too much washing powder in the washing fluid it is costly to operate and wastes washing powder. If there is not enough washing powder in the washing fluid it is not guaranteed that the windshield will be properly cleaned. Therefore, it is also advantageous in such a washing system, where a mixture of washing water and washing powder is supplied, to provide separate tanks for the two fluids and to achieve the mixing proportions by an appropriate construction of the washing system. To this end it has already been suggested to provide a venturi nozzle between a transport pump and the spraying nozzles. The venturi nozzles draw washing powder into the flow of washing water where the two solutions are mixed. However, the presence of the venturi nozzle impedes the flow of the fluid through the fluid supply line. Therefore, in the original equipment of a motor vehicle a stronger pump is necessary. Besides, retrofitting of a motor vehicle involves difficulties, it is necessary to replace both the venturi nozzle and the washing pump. Additionally, the presence of a venturi nozzle generally requires a larger capacity pump than that required on non-venturi systems. Apart from the additional costs caused hereby, it is also questionable, whether this stronger pump can be mounted in the same position as the old pump.